Saturday, January 29, 2011

The FusionTablesLayer in the Google Maps API is a bit of a black box. Fusion Tables generates a clickable tile overlay to use place in your Maps API application, but you don't get direct to change anything. If you want to change data, you have to do server side calls. However, the FusionTablesLayer does give you access to row data on click, which allows you to do interesting things server side.

In my sample interactiveftlayer, I use a Fusion Table of Google's corporate addresses. The table has a simple Color column, with values of 0 or 1. In the Fusion Tables map visualization for the table, I configured the Marker Icon such that values of 0 are green, and 1 are blue. The color means nothing of course about the actual office.

In interactiveftlayer, I suppress the InfoWindow by adding a suppressInfoWindows: true option to the layer initialization. I then add an event listener to the layer that captures the click event on the layer. This gives me row information about the feature clicked. I then send a XMLHttpRequest to the server (in this case App Engine) with the other color (1 if the color is 0, 0 if it is 1). After the response from the XMLHttpRequest, I reload the layer.

There's one tricky part, and hopefully we can find a way to improve this on the Maps API end. The FusionTableLayer is cached by the browser. Which means that even if the data has changed, the layer stays the same, at least at zoom levels visited while it was visible. This includes, BTW, not only the images but the row data associated with them. In order to defeat that caching, I append a Where parameter to the layer selecting for a Id greater than a random number from -1000 to 0. Since I know all Ids are greater than 0, I can do this. I'm not proud of that strategy, but it works.

Tuesday, January 25, 2011

I've posted a couple of times about sliders - Playing with Closure UI Library: Slider and a basic Basic Time Slider in Closure. My final slider example uses the same data set as the last, and incorporates a Two Thumb slider, meaning you can use the slider to set a range of values, not just a less-than or greater-than value. I also corrected something that impacted performance in the last sample, that is I checked whether the query changed by the different events, and change the query on the map layer when the query changes from the last. This is an artifact of the events that I'm listening form, MOUSEUP, MOUSEOUT, and KEYUP. You may remember in the first sample, I realized that firing off a query change whenever the slider had a CHANGE caused too many queries to hit the overlay server, causing the Map to show the missing overlay error. Listening for mouse and key events caused fewer events to fire, but still more than one per change. The change simply tests to see if the new query is different from the old query, and only re-query the layer server if the query changes.

Sunday, January 9, 2011

It's fairly traditional to start a year with either a retrospective of the previous year, or a look forward. Or, of course, both. In that tradition, I'd like to start the year thinking about some trends that I think are going to be important for Geo this year.

Powerful Easy Analysis Tools

This is the year. In 2005, the Google Maps API and Google Earth broadened the use of geography tools far beyond the traditional GIS crowd, sparking a debate between so-called neo- and paleo-geographers that lasted for years. In the last year or so that debate seems to have calmed down a bit, as traditional GIS tools adapted to the web, and neo-geographers, were everywhere. So there's room for a fresh controversy.

The Google Maps API, followed shortly by a host of other APIs from Yahoo!, Microsoft, OpenLayers and others, allowed developers to easily place maps on their site. But as I pointed out in my Ignite Spatial talk in September, developers and GIS professionals aren't the only ones who want to share spatial data. In fact, I'm guessing the vast majority of spatial data, by volume if not quality, is in tabular form. Geocommons has recognized this for years, providing easy tools for uploading, combining, and sharing spatial data. With the addition of Google Fusion Tables, and easy mapping of spreadsheets and sharing of data, powerful tools for data analysis are in the hands of anyone with a Google account. I won't call them "low-end" tools, though certainly they lack the power of ESRI's tools, or any of a host of other proprietary and open source GIS applications. I predict that this year will see a lot of people migrating to Fusion Tables, and others using the API to back-end store the data. Which leads us to

Cloud

OK, I almost had to slap myself for saying "Cloud." After all, of all the buzzwords going around, I think it is the least penetrable to people not "in-the-know" and perhaps has the most number of definitions. To make matters worse, Microsoft has diluted the term even more with this wacked commercial campaign. However, it is being used a lot, so let me be clear, I think this is the year of Cloud Data Hosting.

I predict more and more spatial data will go into "The Cloud." We're already seeing that happening with services like SimpleGeo, Microsoft Azure's support for spatial data, and many other services. Fusion Tables of course has an API which I anticipate will be useful for a number of spatial data storage services.

Cloud Analysis

It's still early days on this. I think that 2011 will be the year of early adoption. In particular, tools like Google Earth Engine will allow you to run high-end analysis in cloud data centers. Some of these tools are already out there, but the introduction of Earth Engine allows you to do things we're used to in the spatial world, namely raster data analysis, but do it faster and cheaper than before.

Location

Well, really, who am I kidding? 2010 was the year of local and location. Facebook's Places and Places API were a very powerful entrance into the location and local scene. Google Places with Hotpot is a big entry into the local market, but it came pretty late in the year. 2010 was about local, 2011 local will become mainstream, such that everyone will have forgotten that it wasn't part of our sites. Remember when there weren't maps everywhere? That was only 6 years ago, now it's taken for granted. Local will get that way by 2012. When of course the world ends, right? That's what the movies tell us anyway.

Prediction posts are fun, because rarely are you held to them. But really they tell you more about where you are now. The things we can't talk about, or don't know about yet, those are the real surprises. Happy New Year everyone.